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ADHD Kids Have Smaller Brains

But Medications Don't Affect Brain Size

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Oct. 8, 2002 -- A new study confirms previous research showing that children with attention deficit hyperactivity disorder (ADHD) have smaller brains than children without the condition. And the study results may put some fears to rest regarding treating young children with medication.

Some parents have voiced concerns that using medication for ADHD in children could harm their brains. But experts say this study takes one step toward reassuring parents that medications, such as Ritalin, do not appear to have a harmful affect on brain size.

In fact, in children with ADHD who did not take medication, one area of the brain was actually smaller. The study is reported in the Oct. 9 issue of The Journal of the American Medical Association.

Researchers report that ADHD children not on medication tested the lowest on some brain size measures as determined by MRI scan. The inner "white matter" area of their brains, which mostly consists of nerve cells and plays a key role in motor coordination, measured 9% smaller compared with ADHD children on medication and 11% smaller than the brains of children without the condition.

The overall brain size was found to be 3% smaller in ADHD children, according to the 10-year study. Specific regions of the brain were also tested and consistently measured smaller in ADHD children. However, there was no distinguishable difference in size or growth patterns in most brain areas between ADHD children who took medication and those who did not. But brain sizes and growth did tend to consistently lag behind children without ADHD.

This study backs earlier findings, including one by the same research team that produced similar results.

"The message for parents is this: What we found is a brain difference in those with ADHD -- not a brain defect," study researcher Jay Giedd, MD, chief of brain imaging at the NIH's Child Psychiatry Branch, tells WebMD. "We never found any damage to the brain in those with ADHD, no foul play or damage or funny business of any kind."

Over a decade, researchers performed multiple MRI brain scans on each of the 152 ADHD and 130 comparison participants, all between 5 and 19 years old. They assessed how ADHD -- and the medications taken for it -- affect brain size and long-term growth.